In natural landscapes, rain that falls on the ground mostly soaks, or infiltrates, into the soil. However, in urban areas, impervious surfaces such as roofs, pavement, and streets, prevent infiltration. This results in an increase in stormwater runoff and pollutants flowing into storm drains, local creeks, and the Bay.

Cities and towns in Santa Clara Valley are working together to create sustainable or green streets, buildings, and parking lots that mimic natural landscapes by incorporating green stormwater infrastructure features. These features allow rainwater runoff to soak into the ground and be filtered by soil. This reduces the quantity of water and pollutants flowing into storm drains and local creeks.

Local municipalities are developing Green Stormwater Infrastructure (GSI) Plans to incorporate green stormwater infrastructure features into new and existing drainage infrastructure on public properties and rights-of-way, including streets, storm drains, and parking lots. SCVURPPP has developed a guidance document (“Green Stormwater Infrastructure Handbook”) to provide guidance to municipal staff on how to incorporate green stormwater infrastructure features into public street, parking lot and park retrofit projects.

Click here for a map of example local projects that have integrated green stormwater infrastructure features. For more information on how green stormwater infrastructure features help our communities, please visit the Green Streets webpage on the Watershed Watch website.

See below for spotlight fact sheets on local and regional Green Street projects

Dispersion of Stormwater Runoff into LandscapingLandscaped areas can be designed to collect stormwater runoff from building roofs and paved areas. Stormwater infiltrates into these areas, and pollutants are filtered out or broken down by the soil and plants.

Bioretention Areas or Rain GardensThese landscaped areas collect, treat, and infiltrate runoff using plants and a specified soil mix. Biotreatment areas can be incorporated into parking lots, curb extensions, park strips, traffic circles, and street edges and medians. Planter boxes next to buildings, tree wells, and tree trenches can also be designed as biotreatment areas.

Rainwater Harvesting and UseRainwater harvesting systems collect and store rainwater for later use. They slow and reduce stormwater runoff, and that stored water can be used for landscape irrigation or toilet flushing.

Green RoofsBuilding roofs covered in soil and vegetation enable rain water infiltration, storage, and evapotranspiration (water loss from soil and plants to the surrounding air). In addition to stormwater benefits, Green roofs can also mitigate urban heat island effects while improving air quality and building energy efficiency.

Pervious Concrete, Porous Asphalt, and Pervious PaversPervious surfaces let rain percolate through them and into the soil. They are generally used in crosswalks, sidewalks, plazas, driveways, parking spaces, street edges, and emergency vehicle access lanes. Pervious surfaces include the following:

Pervious concrete or porous asphalt

Grid pavers with gaps filled with gravel or turf

Interlocking pavers made of pervious material

Solid interlocking pavers that have gaps between

Infiltration TrenchesInfiltration trenches are excavated trenches backfilled with gravel. They capture, store and infiltrate stormwater runoff into the soil. They can be used along street edges and in alleys and parking lots.